Drifting Antarctic Dunes Sign of Changing Climate

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The greatest desert on Earth is not blazing hot but freezing
cold: the icy wastes of Antarctica.

Now scientists find the speed at which sand dunes drift across
the ground of this frigid desert has tripled in the past 40 years
— a finding that could shed light on everything from the planet's
warming climate to deserts on Mars.

Antarctica is not just the coldest
of Earth's continents, but the driest and windiest. The scant
areas that are free of snow and ice make up less than 0.4 percent
of the continental land mass. In places there, the wind has built
sand dunes.

Antarctica has been described as one of the most climatically
sensitive ecosystems on Earth, meaning that one can look at
changes there to help understand global trends in climate,
explained geologist Charlie Bristow at Birkbeck College
University of London. As such, evidence of changes "in the rates
of physical processes that are climatically sensitive, such as
the migration of sand dunes, is important," Bristow told
OurAmazingPlanet.

Scientists also are investigating Antarctic dunes to learn more
about the past; such cold-climate dunes covered large areas of
northwest Europe at the end of the last Ice Age.

In addition, Antarctic dunes could shed light on sand dunes on
planets such as Mars, which is also very cold, dry and free of
surface vegetation.

Bristow and his colleagues used ground-penetrating radar to image
the layers of sand in the Victoria Valley dunes, showing how they
built up over time. The researchers next used optically
stimulated luminescence, a method that determines when objects
were last exposed to daylight, to figure out when specific layers
of sand were buried. This process wasn't always easy.

"One of the problems in the field was the wind, which rises
during the day and becomes quite a problem when the sand starts
to blow," Bristow said.

Five feet a year

The scientists found these dunes apparently are now migrating far
more quickly across the surface than they have for centuries. The
average rate that dunes there have migrated in the past 40 years
is 5 feet (1.5 m) annually. The average annual rate over the
approximately 1,300 years before then was 1.5 feet (0.45 m).

The researchers noted that this speed-up coincides with the
modern
rise in levels of atmospheric carbon dioxide, which traps
heat from the sun and helps warm the planet. A warming climate in
the Dry Valleys would loosen the ice cementing the dune sands in
place, helping them to migrate faster.

In the future, the researchers would like to drill into the
valley's larger dunes to get longer records from older deposits.
They detailed their findings online Aug. 5 in the journal
Geology.